1. Field of the Invention
The present invention relates to a closed loop type fuel cell system with unreacted material removing function, including a recirculating means recirculating unreacted material, such as an oxidant and a reductant, discharged from the main fuel cell back into the main fuel cell; a regenerating means for removing moisture and impurities inside the main fuel cell; and an exhausting means for drawing out the oxidant and the reductant, which are unreacted materials existing inside the regenerating means.
2. Description of Related Art
A fuel cell refers to a system that generates electricity through the reaction of oxygen and fuel (LNG, LPG, hydrogen, methanol, etc.), and simultaneously produces water and heat as by-products. It is an electricity generating device with high electric-generating efficiency and with environmentally harmful substances removed.
And, as to the type of the electrolyte used, there exist a PEMFC (Polymer Electrolyte Membrane Fuel Cell), a DMFC (Direct Methanol Fuel Cell), a PAFC (Phosphoric Acid Fuel Cell), an MCFC (Molt Carbonate Fuel Cell), and a SOFC (Solid Oxide Fuel Cell).
Of such types of fuel cells, PEMFC, PAFC and DMFC are low in operating temperature, each having about 80° C. to 120° C., 190° C. to 200° C., and 25° C. to 90° C., respectively. These are highly available as a power source for a transportation vehicle (for example, automobiles), a house equipment or appliance and portable devices.
Therefore, in order to promote and expand the commercialization of these fuel cells, research attention is focused on the miniaturization, and reducing weight and cost of an entire fuel cell system.
However, since the production of reactants is excessive, and supplying gas into the catalyst layer and diffusing proton into a polymer membrane are prohibited due to a plethora of moisture, in form of water droplets, produced within the operating environment of a high-current area inside a fuel cell, a lowering of fuel cells' performance is observed.
As a more significant problem, a partial cell performance drop on account of uneven water distribution per a unit cell existing in a fuel cell makes it difficult to perform a normal operation.
As such, considering the occurrence of excessive moisture in a fuel cell, referred to as flooding, is an important factor causing the lowering of reaction efficiency, and that it makes the secure operation of fuel cells difficult, it is desperately necessary to discharge excessive moisture out of a fuel cell.
Hence, Korean Intellectual Property Office Patent No. 0509818 discloses “a method and an apparatus for performing an interior purge in a fuel cell system.”
Briefly referring to the prior-art technology, it is configured to possibly detect the voltage of a plurality of cells; purge a moisture and gas mixture, which is existing inside a stack, out of the stack using a pressure difference by controlling a purge valve and a recirculation pump upon a flooding occurrence; and re-supply the gas separated from the moisture back into the stack.
However, such a prior-art technology encompasses following problems.
Firstly, since a fuel purity supplied into a fuel cell fails to reach 100%; and thus, even if the gas separated from the moisture is re-supplied into the fuel cell, impurities stock up inside the fuel cell, lowering generation efficiency.
Also, when carbon, constructing a bipolar plate and an electrode, and impurities such as a metal ion and particles of a peripheral apparatus composing a fuel cell, stock up inside the fuel cell, gradually influencing the durability of the fuel cell as well as producing a current leakage inside it. Consequently, this causes a lifetime shortening or breakage of the fuel cell and produces an enormous repair cost, which seems to be undesirable.
In addition, since a closed circuit is constructed, even if moisture produced in a fuel cell is removed by recirculating gas inside the fuel cell using a conventional technology, impurities influx inside the fuel cell again by means of the gas supplied into the fuel cell, lowering the performance and durability of fuel cells.